Apparatus for desulfurizing ferrous metal

ABSTRACT

AN APPARATUS FOR DESULFURIZING STEEL WHICH PROVIDES A CERAMIC VESSEL CONTAINING A SOLID OR LIQUID DESULFRUIZING REAGENT AND HAVING AN INDUCTOR COIL THERAROUND TO PREHEAT THE VESSEL AND THE REAGENT THEREIN. THE VESSEL IS ADAPTED SO THAT THE MOLTEN STEEL IS POURED THERETHROUGH AND IS DESULFURIZED AS IT PERCOLATED DOWN THROUGH THE REAGENT. THE DESULFURIZED STEEL IS DRAINED FROM THE BOTTOM OF THE VESSEL.

United States Patent 1,292,582 l/19l9 Coulson 266/34 1.4 2.006 10/1923 Jones i. 266/34 1,739,343 12/1929 Baily 75/12 1,739,344 12/1929 Baily 75/12 1,858,386 5/1932 Brace 75/12 1,894,657 l/l933 Baily 75/12 2,572,489 10/1951 Jordan... 266/34 2,921,351 l/l960 Momm 266/42 3,206,301 9/1965 Daubersy 266/34 Primary ExaminerGerald A. Dost Attorney- Forest C. Sexton ABSTRACT: An apparatus for desulfurizing steel which pro vides a ceramic vessel containing a solid or liquid desulfurizing reagent and having an inductor coil therearound to preheat the vessel and the reagent therein. The vessel is adapted so that the molten steel is poured therethrough and is desulfurized as it percolated down through the reagent. The desulfurized steel is drained from the bottom of the vessel.

PATENTED JUN28 l9?! SHEET 3 BF 3 l/V VE N T 0/? RICHARD E. L YMAN Attorney APPARATUS FOR DESULFURIZING FERROUS METAL BACKGROUND OF THE INVENTION This invention relates generally to apparatus for the desulfurizing of steel. More specifically, this invention relates to an internally heated desulfurizing reactor for the batch or continuous desulfurizing of molten steels and steel alloys.

Sulfur in concentrations ranging from 0.005 to 0.05 percent by weight is always present in commercially produced steels and alloy steels. Except in special free-machining applications, sulfur is considered and undesirable contaminate because of its detrimental effect on the mechanical properties of steel. Because these detrimental effects increase with increasing sulfur concentrations, there is considerable effort and expense devoted to keeping sulfur content as low as possible during smelting of iron ore and the subsequent conversion of molten iron to steel or alloy steel. Since it is usually impossible to avoid substantial sulfur contamination during the reduction of iron ore by existing smelting and direct reduction processes, it is nearly always necessary to remove sulfur from the molten metal during subsequent processing to produce steel.

According to existing technology, sulfur removal is usually accomplished by reacting the molten steel with a basic slag in the steelmaking furnace, or by injecting pulverized reactants such as lime, CaO, or calcium carbide, CaC into the molten metal by entrainment in a jet of argon, nitrogen, or some other inert gas. These existing methods of desulfurizing are limited in effectiveness and are suitable only to batch processing of steel. It would be difficult to utilize either of these methods in tandem or with a continuous smelting or steelmaking processes.

SUMMARY OF THE INVENTION This invention is predicated upon my conception and development of an independent reactor apparatus for the desulfurizing of steel which may be adapted to batch or continuous processes. The reactor apparatus is self-heating and is adapted to contain a solid or liquid desulfurizing reagent. Molten steel poured through the reactor apparatus is desulfurized as it passes in contact with the desulfurizing reagent therein. If a batch process is desired, the desulfurizing reagent is stationary within the reactor. If a continuous process is desired, the desulfurizing reagent is caused to flow through the reactor apparatus countercurrent to the flow of the molten steel.

Accordingly, it is a primary object of this invention to provide a reactor apparatus for desulfurizing steel which may be adapted to batch or continuous processes, and may be used in tandem with continuous smelting or steelmaking processes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational cross section of a desulfurizing reactor according to one embodiment of this invention. In this embodiment a solid desulfurizing reagent is utilized for batch process desulfurization;

FIG. 2 is an elevational cross section substantially the same as that shown in FIG. 1 except that this embodiment is adapted for the use of a liquid-desulfurizing reagent in a batch process; and

FIG. 3 is an elevational cross section of a desulfurizing reactor according to a third embodiment of this invention wherein a liquid desulfurizing reagent is utilized in a continuous desulfurizing process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, one embodiment of this invention comprises a substantially cylindrical, open-topped ceramic vessel 10, having a restricted outlet 11 in the bottom portion thereof. Vessel must be manufactured of some electrically conductive structural refractory material such as graphite. The interior wall surfaces of the refractory vessel 10 and the outlet 11 may be lined with a suitable refractory ceramic material 12 such as is used in the crucibles of steelmaking induction furnaces. The outer cylindrical periphery of ceramic vessel 10 is limited with a suitable high-temperature thermal insulation material 13. Vessel 10 and the inner and outer linings thereon are supported between a pair of reinforced refractory seats 14 and 15 at the top and base respectively. Refractory seat 14 is provided with an axial opening 16 which substantially mates with the opening in the top of vessel 10, while refractory seat 15 is provided with an axial opening 17 which substantially mates with outlet 11.

The entire refractory structure described above is braced within a trunnion-mounted metallic frame structure which comprises a pair of parallel 'end plates 20 and 21 rigidly spaced by at least two beams 22. End plates 20 and 21 are provided with openings 23 and 24 respectively which coincide with openings 16 and 17 in the refractory seats 14 and 15 respectively. A pair of opposed trunnions 25 rigidly secured to beams 22 support the frame structure between a pair of trunnion stands 26. Hence, the entire structure may be pivotedat trunnions 25 to invert the reactor and dump its contents.

A removable inlet refractory plug Plug is fitted into the coincident openings 16 and 23. Plug 30 is provided with an axial funnel opening 31 therethrough so that molten steel may be poured into the lined vessel 10. A removable outlet refractory spout 32 having an opening 33 therethrough, is fitted into coincident openings 17 and 24. Since this refractory spout 32 is inverted, it may be necessary to provide a lock ring 34 to keep spout 32 in place.

Vessel 10 is internally heated by an inductor coil 35 circumferentially surrounding insulation material 13. Such an external source of heat is necessary to prevent thermal loss from the molten steel during desulfurization. The inductor coil must of course be secured to a power source (not shown) which should be sufficient to heat the graphite vessel 10 to a temperature of about 3,000 F.

To operate the above-described desulfurizing reactor, inlet refractory plug 30 must be removed and vessel 10 charged with a suitable solid desulfurizing reagent 37 such as crushed calcium carbide or briquetted burnt lime. Depending upon the particle size of the reagent 37, it may be necessary to employ some form of refractory grid (not shown) at the mouth of outlet 11 to keep the reagent 37 from falling therethrough. When the vessel 10 has been so charged, inlet refractory plug is replaced. A receiving vessel 39 must be positioned beneath the outlet spout 32. The receiving vessel 39 may be a hot metal ladle, a mixer, a steelmaking furnace, a teeming ladle, or a tundish as appropriate to the smelting or steelmaking process involved.

After the vessel 19 and its contents have been heated to temperature of 2,400 to 3,000 E, the molten steel to be desulfurized is poured into the reactor via inlet refractory plug 30. As the molten steel moves downward percolating through the reagent 37, it is effectively desulfurized before it emerges through outlet spout 32 and into receiving vessel 39.

During the process, inlet plug 30 prevents the reagent 37 from floating upward as it is made buoyant by penetration of the molten steel.

In a batch process, such as the treatment of a ladle of mo!- ten steel, the quantity of reactant 37 charged into the reactor will be sufficient to process 1, 2 or some other integral number of batches. When reactant 37 has become spent and it is necessary to recharge the reactor, inlet plug 30 is removed and the reactor rotated about trunnions 25 to dump the spent contents.

A second embodiment as illustrated by FIG. 2 is substantially similar to the FIG. I embodiment detailed above except tion of vessel 10. The distributor block 42 is provided with a plurality of small holes 43 therethrough which distributes the molten steel in a plurality of small streams into the molten slag. This is done so that a greater contact surface area is created to assure sufficient desulfurization.

In operation, the liquid reactants are charged into the vessel while valve 40 is closed. When the liquid reactant is at a suitable temperature, molten steel is poured into the reactor via inlet plug 30. In this second embodiment however, the molten metal is first collected on top of distributor block 42 while a plurality of small streams of metal pour through holes 43 into the liquid reactant below. After the molten steel has percolated down through the desulfurizing reagent it will form a pool 47 in the lower portion of the reactor, floating the liquid reactant thereabove. Before the liquid reactant reaches the distributor block 42, valve 40 should be opened to permit the desulfurized metal to flow into receiving vessel 39. The opening of valve 40 should be carefully throttled to maintain pool 47 at a reasonably constant level thus preventing anyv liquid reactant from draining through valve 40.

As in the FIG. 1 embodiment, the liquid reactant in this FIG. 2 embodiment should be sufficient to desulfurize an integral number of batches. Thereafter, when the liquid reactant is spent it must be dumped or drained from the reactor and replaced by fresh reactant.

It is apparent that the two embodiments described above are not by themselves continuous devices. Nevertheless, either embodiment could be used in a continuous system if installed in a battery of two or more reactors. Thus, when the reactant in one reactor becomes spent, the molten steel feed would be diverted to the next reactor while the first is being recharged and so on.

A third embodiment as illustrated by FIG. 3 is substantially similar to the FIG. 2 embodiment except that it is modified for a fully continuous operation, in that liquid desulfurizing reagents are continuously charged through the reactor while the steel is being desulfurized. This embodiment requires a modified vessel 50 having a reactant inlet duct 51 to admit fresh liquid reactant to the lower inner portion of vessel 50. As shown in FIG. 3, inlet duct 51 is vertically disposed within the cylindrical wall portion of graphite vessel 50 communicating between the lower inner portion of the vessel and the upper surface thereof. In addition, a substantially horizontal reactant outlet drain 52 is provided through the entire insulated vessel 50 and the induction coil 35. A replaceable refractory outlet spout 53 may be provided at reactant outlet drain 52. A modified inlet refractory plug 54 is also utilized to provide a funneled reactant inlet 55 as well as a molten steel inlet 56.

In operation, the FIG. 3 embodiment functions substantially the same as the FIG. 2 embodiment except that the liquid reactant is continuously being replenished for continuous operation. To start the process, valve 40 must of course be closed. The vessel 50 is then filled with liquid reactants which are continually admitted via inlet duct 51 from some source such as trough 57. Excess reactant overflows through outlet drain 52 and is collected and carried away by any means such as trough 58. As in the FIG. 2 embodiment, the molten steel-to be desulfurized is poured into vessel 50 where it first collects on top of distributor block 42. Small streams of molten steel then issue through holes 43 and percolate down through the liquid reactant. The desulfurized steel is collected in a pool 47 in the lower portion of the reactor, below the outlet portion of duct 51, floating the liquid reactant thereabove. Here again valve 40 must be controlled to prevent the liquid reactant from draining therethrough.

Accordingly, the steel is desulfurized as it percolates downward through the upward moving liquid reactant. The reactant must of course be supplied through duct 51 at a rate sufiicient to insure continued desulfurization of the molten metal. That is to say, if the liquid reactant is replenished at a rate at least as fast as it is becoming spent, the process may be operated continuously.

I claim: 1. Apparatus for desulfurizing molten steel comprising a refractory lined graphite vessel having a chamber therein for receiving a molten desulfurizing reagent, said vessel having a top'opening for admitting molten steel into said chamber and a bottom opening for discharging the molten steel from said chamber, a throttle valve associated with said bottom opening to regulate the discharge therethrough, a distributor block having a plurality of vertical holes therethrough secured across the upper portion of said chamber to distribute said molten steel into said chamber as a plurality of small streams emerging through said holes, and an inductor coil disposed around said vessel to heat said vessel and the reagent and steel therein.

2. Apparatus for desulfurizing steel according to claim 1 including a reactant inlet duct near the lower portion of the vessel and a reactant outlet drain through a wall of the vessel near the top thereof, whereby said liquid desulfurizing reagent can continuously be circulated through said vessel.

3. Apparatus for desulfurizing steel according to claim 2 wherein said reactant inlet duct comprises a vertical opening through a wall portion of said vessel communicating between the lower inner portion of said vessel and the upper surface thereof. 

